Dyno Disappointment.....

[arsey30]

Not only larger jets in UK carbs but the richer ones in the fronts, not rear like Japanse spec bike. Why?
The emulsion tubes are different too.

I think that info is wrong Uk bikes are 120F and 122R, see Cammo's guide for details

I can only go by the Honda workshop manual and the parts book.
The jets were fitted that way when I bought the bike, but not sure if carbs had been off before

[philfingers]

i'm only going on what i've learnt on this forum the last four weeks or so, I may well be wrong and if so i apologise, it was in th carb jetting guide (the sticky)

[arsey30]

It is rumoured that the UK bike's exhaust is free-er flowing. But even then, it would have to be some kind of magical baffling system to be more open than a full system on a JDM bike. Has anyone spotted differences in the airbox? It does have an oil cooler so maybe it runs cooler? This would maybe require a little more fuel? Other than that there must be some pretty big differences in the carbs.

I have not compared carbs or aribox on UK/Jap bikes as I have only worked on one a time, but the parts lists detail different components.
The airbox question makes sense as that is one way to get the extra power [62hp] and would account for jetting.
Part of the the RC30 restriction is a smaller airbox snorkel.

edit. The parts books show the airboxes to be the same.
Would still like to know where the extra 4hp comes from though.

[porndoguk]

i'm only going on what i've learnt on this forum the last four weeks or so, I may well be wrong and if so i apologise, it was in th carb jetting guide (the sticky)

FINGERS,

Dave knows his shit

uks had bigger fronts pal :D

[arsey30]

i

FINGERS,

Dave knows his shit

uks had bigger fronts pal :D

When working on bikes, I find it best to believe nothing I hear and only half of what I see

[philfingers]

i'm only going on this, page 1 viewtopic.php?f=24&t=14524 :-)

[Neosophist]

It is rumoured that the UK bike's exhaust is free-er flowing. But even then, it would have to be some kind of magical baffling system to be more open than a full system on a JDM bike. Has anyone spotted differences in the airbox? It does have an oil cooler so maybe it runs cooler? This would maybe require a little more fuel? Other than that there must be some pretty big differences in the carbs.

I have not compared carbs or aribox on UK/Jap bikes as I have only worked on one a time, but the parts lists detail different components.
The airbox question makes sense as that is one way to get the extra power [62hp] and would account for jetting.
Part of the the RC30 restriction is a smaller airbox snorkel.

edit. The parts books show the airboxes to be the same.
Would still like to know where the extra 4hp comes from though.

Yep, interesting one.

59ps JDM spec and 63ps UK spec (according to sales brocheures)

The ZXR400-L UK spec made 65ps vs 59ps for the JDM bike, differences here were bigger carbs (32mm vs 30mm) and different grinds of cams, the ignition box may also have a different advance / retard but it's not known for definate.

Is the UK ignition box any different on a UK bike?

Carb wise:

122 go in the FRONT
120 in the rear.

Emulsion Tubes:

UK Bikes:

Front: 16165MR8600
Rear: 16165MR8640

JDM Bikes:

Rear: (All models) 16165-ML0-721 - NC24 part..
Front:

K and some L: 16165-MN4-003 - CBR600FH Part
Some L and all N: 16165-MR8-780 - NC30 part

CV Piston (Slide)

UK Bikes: 16111MR8600
JDM Bikes: (all models) 16111-MR8-003

Needles:

UK Bikes:

Front: 16151MR8600
Rear: 16151MR8640

JDM Bikes:

Front: 16151-MR8-003
Rear: 16152-MR8-003

* Interesting to note that both front and rear emulsion tubes for the UK model are unique to UK bikes, along with slides and needles while only the later N model had a unique front emulsion tube (different to the UK bike again), depending on JD model the emulsion tube was originally made for NC24 or CBR600.


The exhausts are different part numbers though for the rear-section.

UK Bike: 18300MR8601
JDM Bike: 18300-MR8-003 (K) 18300-MR8-780 (L)/(N)

Camshafts are same on all models.

Ignition boxes are different but this may just be to bypass the 180km/h / 5500rpm restriction

UK Bike: 30400MR8600
JDM Bike: 30400-MR8-004 (same on all models)

In regards to the air-box.

Airbox Lid:

UK Bike: 17221MR8010 (same as JDM L/N)
JDM Bike:
(K) 17221-MR8-000
(L/N) 17221-MR8-010

The lower base-plate is different on all models, no idea what was changed.

UK Bike: 17230-MR8-020 (Same as JDM N)

JDM Bikes:
(K) 17230-MR8-000
(L) 17230-MR8-010
(N) 17230-MR8-020

So in effect the UK airbox is the same as the later JDM (N) model.

Engine Wise:

Conrods are the same on all motors (NC24 con-rods)

Pistons are the same too except the JDM (K) model had an earlier revision upto a certain Serial number.

Early JDM (K) 13101-MR8-000
Later K onwards and UK bike: 13101-MR8-010

So perhaps it is just a less restrictive exhaust and larger lets and carb tweeks (and maybe ignition box?). It isn't uncommon to see health NC's producing 62/63hp with a race-can and larger jets. Sounds like a recreation of the UK spec to me.. perhaps explain why people often get awkard flat-spots when running a race-can with JDM carbs and larger jets, maybe they were 'tuned' out of the UK model by means of different needles and emulsion tubes.

Would be nice to get hold of an unmolested set of carbs and rear exhaust section to see as it's the only main differences.

Will have to see what mine makes with the Yamamoto system on it soon (as it's had bigger jets) and I don't have flat-spots *yay*

[philfingers]

isn't std Japanese unleaded a higher octane than std (at that time) UK unleaded, so in effect you'd need smaller jets for the same calorific value, if that's the right (weight watchers!) term!

[hunter]

It's a long time ago now but when i played around with my ukNC. and an import track bike i did notice some difference in the cdi wire colours.Bet they are different part numbers.

[Cammo]

It's a long time ago now but when i played around with my ukNC. and an import track bike i did notice some difference in the cdi wire colours.Bet they are different part numbers.

The Uk bike will probably have no speed limiter which is controlled by the cdi.